Transformer-coupled π-network differential CMOS oscillator circuit topology

This paper reports a novel oscillator circuit topology based on a transformer-coupled π-network. As a case study, the proposed oscillator topology has been designed and studied for 60GHz applications in the frame of the emerging fifth generation wireless communications. The analytical expression of the oscillation frequency is derived and validated through circuit simulations. The root-locus analysis shows that oscillations occur only at that resonant frequency of the LC tank. Moreover, a closed-form expression for the quality factor Q of the LC tank is derived which shows the enhancement of the equivalent quality factor of the LC tank due to the transformer-coupling. Last, a phase noise analysis is reported and the analytical expressions of phase noise due to flicker and thermal noise sources are derived and validated by the results obtained through SpectreRF simulations in the Cadence design environment with a 28nm CMOS process design kit commercially available. Copyright © 2016 John Wiley & Sons, Ltd.